1. Field of the Invention
The present invention relates to a method for removing debris from a well-bore, and more particularly, to the use of a liquid suspension containing hydrophilic fibers to sweep debris from the bore.
2. Description of the Background of the Invention
Oil, gas and other subterranean wells are made by drilling a borehole into the ground. As the rotating drill works its way through the geological formations, the drill becomes hot and debris from the cuttings, such as rock, dirt and clay, accumulates, filling the hole. To cool and lubricate the drill and remove the build up of drill cuttings from the borehole, various methods have been used. Typically, fresh water, salt water, or a water/oil mixture is used to flush the cuttings from the well-bore and to cool the drill. However, the liquid alone does not remove enough debris. To improve the levels of debris removal, additives are injected with the liquid through the drill pipe into the well-bore. The liquid is forced through the annulus created between the drill pipe and the wall of the borehole to carry the debris out of the borehole and simultaneously to cool and lubricate the drill.
A variety of additives have been used with drilling liquids. Viscosifiers, such as bentonite clay, Fullers' earth (attipigulite clay) and polyacrylamide fibers are dissolved in the liquid to increase its viscosity. Other materials, such as asbestos fibers, cotton seed fibers, wood cellulose and crushed peanut hulls, have been dispersed in the liquid. The latter group of additives do not dissolve. Some of these additives have been observed to work well in fresh water but do not work well, or at all, in salt water.
Another reason to include additives is to prevent fluid loss through fissures and pores in the geologic formations. Significant amounts of liquid injected into the well bore can be lost through porous rock or open channels in the formations. Additives sometimes function to stem the loss of circulation fluid by sealing the porosity and channel openings of the formations.
The addition of these materials, however, slows the penetration of the drill through the earth. Slower penetration leads to increased operation time, higher energy costs, increased use of liquid and increased use of additives for the additional liquid.
There is a need for a method of cleaning well-bores which will not retard penetration of the drill and will not result in increased time and energy costs. There is a further need for a method which works to remove the debris whether the liquid used is fresh or salt water, or oil based.